1. Field of the Invention
This invention relates to the operation of a measuring device which utilises the breaking or restoring of a beam of radiation for detection of an object, particularly but not exclusively a measuring device for use as a cutting tool detector having a-radiation transmitter for transmitting a beam of radiation and a radiation detector spaced from the transmitter for detecting the beam of radiation.
2. Description of Related Art
Measuring devices of the type mentioned above are known. One such device is described in U.S. Pat. No. 6,496,273. The optical apparatus described is designed principally for use in detecting cutting tools on machine tools and is capable of very precise measurement.
In order to increase the versatility of the device shown in the above patent the light transmitter and light detector are required to be spaced at varying distances. Large tools require a greater distance between the transmitter and the detector than the distance required for a small tool so that they can fit in between the transmitter and the detector. A large machine tool may need a large distance between the transmitter and the detector so that a tool can be measured anywhere in the beam without it being necessary to traverse the tool long distances to a specific measuring location. Small machine tools do not have the space to include a lengthy measuring device which has a large distance between the transmitter and the detector.
Consequential adjustments in the gain of the amplifiers at the detector have to be made when the distance between the transmitter and the detector are varied. In practice gain is adjusted by removing a cover to obtain access to switches within the detector housing which are used to select the required gain based on the distance between the detector and the transmitter.
Problems occur when the user fails to replace the cover correctly or leaves contamination within the housing. Also the user can cause damage to the circuitry inside the housing or set the switches incorrectly. Other known commercially available systems use potentiometers instead of switches to adjust the gain, but such systems suffer the same drawbacks.
Thus a permanently sealed system would be advantageous but would not allow for conventional adjustment of detector amplifier gain.